The role of time and mixing in the degradation of terrestrial derived dissolved organic carbon in lakes of varying trophic status

Abstract

The processing of dissolved organic carbon (DOC) in lakes has important implications for aquatic metabolism, temperature, and how organisms respond to sunlight. In temperate lakes, few studies have focused on the degradation of terrestrially derived dissolved organic carbon (tDOC). Here, we conducted three experiments to evaluate the long-term response to both photodegradation and biodegradation of tDOC, the short-term response to the photodegradation of tDOC, and the effects of mixing tDOC with surface water from each lake. We measured changes in DOC concentration and colored dissolved organic matter (CDOM) due to photo and or biodegradation in three lakes of varying trophic status. Results showed that tDOC is capable of being photodegraded up to 90 days and that biodegradation can take up 20 days to become relevant in certain systems. The short-term experiment depicted variable changes in each lake. Mixing surface and ground water together in varying ratios provided a clear response pattern in Lake Lacawac, but not in the other lakes.